1. Field of the Invention
This invention relates to a heated pizza or food delivery system including food catering. This system keeps pizzas or food to be warm once out of the oven by a heater placed either in a bag or stand alone with a cover while being continuously heated by power from a wall power outlet, a car socket, or a battery, without using external power adapters.
2. Discussion of Background Information
Traditionally, food is delivered in an insulated container. The purpose is to keep food hot and tasty and retain attributes such as crispiness, texture, etc. Thin crust and gourmet pizzas require steady temperature regulation for its entire period after it has come out of the oven. In order to minimize bacteria growth, the Food and Drug Administration recommends keeping food at a temperature of at least 140 F. Temperatures above 190 F are considered active cooking for many foods; temperature regulation between 140 F and 190 F therefore is the optimal temperature range for food delivery.
Heated food delivery systems were initiated by Harold D. Solomon in U.S. Pat. No. 4,816,646 with a quick disconnect between the heater and the power source. However, despite several inventions that come later with an attempt to address the same problem; these solutions have not yet met the practical aspects and reliability required by a heated delivery system. A true heated delivery system requires a totally integrated solution, where it has to be portable, light-weight, amply spacious for food storage, temperature regulated, and continuously heated delivery solution for all situations—in stores, vehicles, and even places without a ready available power outlet.
In order to address the issue of power cables breaking in their quick disconnect systems, C. Owens et al. U.S. Pat. No. 6,989,517, U.S. Pat. No. 6,861,628, U.S. Pat. No. 6,555,789, U.S. Pat. No. 6,433,313, U.S. Pat. No. 6,392,201, U.S. Pat. No. 6,384,387, U.S. Pat. No. 6,121,578, and Brian L. Clothier et al., U.S. Pat. No. 6,504,135, U.S. Pat. No. 6,444,961, U.S. Pat. No. 6,232,585, replace the cable attachment to an external power source with an inductive heating solution. It can come in a form of conductive coils connected to a resistive heating element or passive induction plates that is heated by the magnetic induction charging station. However, in a typical delivery, it is common to find several orders packed in the same delivery bag. Each time the bag is opened for a delivery, the temperature inside the bag falls quickly; as you travel further delivery distances without a continuous power source to power the heater in the vehicle, the temperature cannot be maintained. In order to pack more energy stored in these induction plates, many of these heated plates reach temperatures above 200 F and as high as 240 F, exceeding the boiling point of water. Temperatures above 190 F are considered cooking the pizza. Such temperatures far exceed the recommended temperature for keeping pizzas, buffets, and other food warm and can change the food properties.
In a typical catering event where the food is left on display for a few hours, the inductive heating solution is inadequate. Inductive heater plates need to be profiled every six months because they do not maintain the same temperature profile after repeated use. Many have failed miserably when the peak temperature rises uncontrollably, burning holes in the insulated bags they are stored in.
William M. Bostic et al., U.S. Pat. No. 6,486,443, U.S. Pat. No. 6,060,696, U.S. Pat. No. 5,880,435, Sigurd Frohlich, U.S. Pat. No. 5,884,006 and Wayne Baldwin et al., U.S. Pat. No. 6,936,791 use phase change technology to release stored heat, but this also runs into the same problem as the induction heating, since the stored energy is quickly depleted after an extended period of use.
The challenge of continuously using an external electrical power source for heating up the heater lies in finding a good and reliable quick disconnect solution in addition to a lightweight, uniformly heating, thin, and large area heater requirement. However, typical power cables used for such devices have joints and connectors that are subject to repeated stress from repeated connection and disconnection of the cables. In heating environments, the heat communicates to the power cords, which are typically made of plastic, making them particularly vulnerable to damage from this induced stress. These cables thus often break under such stress, which discourages store owners from using these heaters.
This problem is compounded when the heater is designed for the 12V DC vehicle outlet. When the heater is in the store, where the wall outlet of 110V is used, a power adapter is required to convert 110V AC to 12V DC. Robert Check, U.S. Pat. No. 6,018,143 describes the use of a low voltage transformer in a restaurant. A power adapter adds further weight to the system, making the cord system even more complicated and fragile.
William Lee Duke et al. U.S. Pat. No. 6,222,987, even mentions that the connector has to be for a greater amperage outlet, since he includes a fan too.
This receptacle and power adapter problem is compounded when twenty or thirty bags are all powered at the same time. The typical solution involves a big transformer with several outlets, with one outlet for each bag. The use of a Power Distribution Unit or special power rack becomes a necessity. This extra equipment is a burden for a small store where space is a premium. The bags' heavy electrical power draw also requires a special high power electrical installation for each store. This implies that the use of the heated bags solution be fixed at the location of the store where the high power wall outlet is available and makes the store's renovation a nightmare, due to these constraints.
Arkady Kochman et al. U.S. Pat. No. 6,452,138, U.S. Pat. No. 6,403,935, U.S. Pat. No. 6,369,369, U.S. Pat. No. 6,229,123 describes the use of conductive textiles and threads as heating elements. Conductive threads do not heat large areas uniformly because the diameter of the threads is very small. The large diameter PTC heated fibers/wires found in heated blankets can be used as heating elements. They are usually very stiff with grid patterns, with a large space between fibers/wires, therefore creating a very uneven heat distribution. In total, these technologies do not address the qualities provided by a large area heater with a uniform heating profile.